Radio tuning device



.Fuly 1, 1930.

o. E. MARVEL RADIO TUNING DEVICE Filed Jan. 7;" 1927 A TTORNEYS.

Patented July 1, 1930 ORIN E. MARVEL, DAYTON, OHIO, ASSIGNOR. BY MESNE ASSIGNMENTS, TO GENERAL MOTORS RADIO CORPORATION, OF DAYTON,

OHIO, A COREORATION OF OHIO RADIO TUNING DEVICE This invention relates to the tuning of radio frequency circuits and more particularly to a tuning element adapted to bring a radio frequency circuit into resonance.

One object of the invention is to provide in the tuning of radio circuits, for conductively coupling a tuning device to an aperiodic circuit to bring the circuit into resonance at any desired wave-length throughout any predetermined band of radio freqencies.

In one embodiment of the invention disclosed herein a variable capacitance or inductance or a combination of capacitance and inductance 'is conductively coupled both to and aperiodic primary circuit and a grid circuit of an audion tube to simultaneously bring these combined circuits into resonance. The tuning element is particularly adapted to cooperate with a circuit in which a radio frequency choke having a high effective resistance at the customary radio frequency wave-lengths is used for impressing oscilla tions received in the primary circuit on the grid of an audion tube.

Other objects and advantages of the invention will be more fully set forth in the following description, in the claims, and in the drawings in whic Fig. l is a diagrammatic showing of the invention showing a capacitance and inductance conductively connected across a radio frequency choke in a combined antenna and grid circuit;

Fig. 2- is -a diagrammatic showing of a a modification of the invention in which the capacitance and the inductance are connected in series across the radio frequency choke;

Fig. 3 shows a further modification of the invention showing the tuning device connected across a radio frequency transforming coil in a grid circuit;

Fig. 4 is a side view showing the tuning element as an attachment connected to a radioreceiving set;

Fig. 5 is a side elevation of a form of tuning device in which the capacitance and the inductance are simultaneously varied in a proportionate manner; and

Fig. 6 shows the manner in which the 50 capacitance and the inductance are coupled together on the same shaft so as to be simultaneously varied. Referring more particularly to the drawlngs in which similar reference numerals represent corresponding parts in the various figures, one form of the invention is shown in Fig. 1 in which an audion tube designated generally 10 is provided with a grid 11 on which electrical oscillations are impressed so as to govern an output circuit 12 connected to the anode or plate 13 of the tube. The filament 14 of the tube is adapted to be heated from a battery or any suitable source of current not shown, so as to cause the emission of electrons in the customary maner well known in the art.

The grid 11 is connected by a wire 15 to the antenna 16 and a radio frequency choke 17 having a high effective resistance at the customary wave-lengths used in ordinary broadcasting reception is connected to the an tenna and to the grid wires at 18. The opposite end 19 of the choke 17 is connected to the ground at 20 and connected to the wire 21 which leads to the filament 14 of the audion tu e.

The radio frequency choke preferably consists of a large number of turns of small diameter fine wire so that its efiective resistance at radio frequencies is in the neighborhood of 1,000,000 ohms, and the winding is preferably such as to produce an effective distributed capacity of a substantial value, represented in dotted lines at The choke 17 in the combined antenna and grid circuits will thus operate to connect the aerial to the ground so that a comparatively high voltage may be impressed on the grid 11 of the audion tube, the antenna and grid circuits however being adapted to operate aperiodically by reason of the extremely high impedance or effective resistance of the choke 17 In order to decrease the resistance of the path of the radio frequency waves between the antenna and the ground and also tune the grid circuit of the audion tube 10, a tuning device designated generally 30. is connected across the. points 18 and 19 of the circuit. This tuning device consists ofa variable capacitance 31 connected in parallel with a variable inductance 32 which are of such values that the combined aperiodic or primary capacitance 31 consisting of a serles of movable plates 33 and fixed or stator lates 34, the movable plates 33 being attached 40 which is operated by a hand-operated controlling element 35 located, as shown in Fig.

5, on the front of the mounter case 36 so as to be easily accessible for tuning the apparatus.

The same shaft 40 which bears the movable plates of the condenser 31 also bears the rotor inductance coil 41 which is connected in series with the fixed or stator coil 42 of the inductance so that the inductance and the capacity of the parts 32 and 31 may be simultaneously increased or decreased in unison and in a proportionate manner to maintain the power factor of the circuits at a maximum value. The inductance 32 and the capacitance 31 are adapted to be so varied that when tuned they will bring the combined antenna and grid circuit comprised of the antenna path to ground and the grid input path simultaneously into resonance corres onding to the articular wave;length to WhlCh they are ad usted and thus'permit both of these circuit paths to operate more efiiciently and selectively, and to increase the volume of the signals of the radio receiving or transmitting set with which the tunin device is used. The values 'of the capacitance 31 and inductance 32 are such ing that they may be adjusted simultaneously to positions where the effective resistance at radio frequency of the combined tuning device is a very high value so that the antenna circuit and the grid circuit may operate device. When t aperiodically the tuned condition of the grid circuit is no longer present as both the condenser and the inductance then offer high effective resistance in an untuned manner, to radio frequency oscillations. Thus-incoming radio signals may be impressed by means of the choke coil on the grid 11 of the audion tube due to the aperiodic manner in which the circuits function with the tunin device untuned. The effective distribute capacity 25 of the radio frequency choke-17 is of a comparatively small value and is preferably insuflicient to tune the grid or-antenna circuits except for wave-lengths greater than those adapted to be received. The choke 17 is adapted to provide a path from the antenna.

to the ground of somewhat lesseffective'resistance for those radio frequencies of comparatively .low wave-lengths to permit some of the energy to escape at these low waveto the shaft aperiodically althouglh connected to the tun-' e grid circuit operates.

are connected, and which are adapted to be quickly attached or connected to the radio set with which the attachment is to be used.

Obviously it is unnecessary toconnect the capacitance and the inductance together exactly as shown in Fig. 1 as-just described although it is preferred to adjust the capacitance and the inductance of the tuning device in unison only one of these tuning elements may be operable to bring the antenna and the grid paths into resonance.

In Fig. 2 a modification of the invention is shown in which the grid 50 of the audion tube 51 is connected to a radio frequency choke 52 havin a distributed capacity represented in dotte lines at 53. The antenna 54 instead of bein connected directly to the end 55 of the cho e 52 is connected to the tuning device represented generally by the'numeral 56, this antenna wire being connected first to a va riable condenser- 57 so that the different characteristics of antennae of various lengths may be compensated to permit the use of a smaller tunin condenser 61. capacitance 61 is preferably variable and is connected in series in the modification shown in Fig. 2 with the variable inductance 63 which is connected at one end to the adjustable condenser 57 and to the grid circuit of and The condenser or the audion tube 51 at the point 55. The untuned antenna circuit through the condenser 57,.the grid path and the radio frequency choke 52 to the ground at 64 may thus operate aperiodically when the values of the capacitance 61 and the inductance 63 are ad justed to provide a path having a high radio frequency effective resistance. When how- .ever the tuning elements 61 and 63 are adthe antenna and grid with the untuned aperiodic operation of these circuits when other tuning devices of the radio set such as the tuning elements 60 shown in Fig. 4 are operated to bring in any desired signal.

In Fig. 3 another embodiment of the invention is shown in which the variable tuning device'designated generally 70 consists of a variable capacitance 71' and an inductance 7 2 cooperating therewith, these tuning elements being connected across a part 73 of a radio frequency transformer coil 74 provided in the grid circuit 75 of the audion tube 76. The antenna wire 77 is connected at the point 78 to the transformer coil 74 and to the tuning elements 71 and 72 so that the normally operating aperiodic antenna circuit through the part 73 of the coil 74, leading to the ground 79, may be brought into resonance or tuned to any desirable wave-length so as to increase the currents flowing through the coil part 73 which by the usual transformer action will cause a greater voltage being impressed on the grid circuit 75 of the audion tube. A radio frequency choke 80 is shown conductively connected across the coil 74 and the grid circuit path for permitting the aperiodic operation of the grid circuit, such operation of the choke 80 not interfering with the tuned operation of the circuits when the tuning elements 71 and 72 are in their tuning relation.

The various tubes 76 and 85 together with othef tubes which may be connected to the output of the tube 85 are shown coupled together so that-the output circuit of the tube 76 is inductively connected to the grid or input circuit 86 of tube 85 and the output circuit 87 connected to the plate 88 of tube 85 is inductively coupled to the succeeding tube or tubes.

,The circuit 86 of the tube 85 is shown as including the radio frequency choke coil 89 connected across the grid circuit and the.

brought into resonance for any wave-length received by the set by adjustment of the tuning device 92, corresponding to the tuning device 30 of Fig. 1 and consisting preferably of a tuning condenser or a combined tuning condenser and impedance variable together as previously described. After the desired sending station has been tuned in by adjustment of the various dials which operate the tuning elements in the various tuned circuits of the set, the combined condenser and impedance tuner located in the aerial circuit or in the other aperiodic circuits of the set may be adjusted to regulate the volume of the received signal and attain the maximum efficiency of operation. WVhen the tuning devices represented at 60 in Fig. 4 of the various tuned circuits of the receiving set designated generally at 90 in this figure, are simultaneously operated to adjust the various tuned circuits of the receiving sets proper to bring in a desired transmitting station the tuning device connected to the aperiodic circuits are adjusted so that they have comparatively high effective resistances at radio frequen-' cies so as not to disturb the aperiodic opera-- tion of these circuits. After the various dials 60 of the receiving set have been properly adjusted to obtain maximum value of the signal then the untuned circuit or circuits may be tuned or brought into resonance for the desired signal by a proper manipulation of the controlling dials 35 and the volume of reception may be regulated to any desired amount by further manipulation of these dials.

While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is: v

1. In combination with a radio-receiver set having an aperiodic antenna circuit containinga radio frequency choke with a grid circuit connected across said choke, atunlng attachment for said setcomprising a tuning element independent of said choke and embodying an inductance and a condenser, means for quickly conductively attaching said tuning element to the antenna and the grid circuits, and means for adjusting the tuning element to bring the antenna circuit into resonance.

2.. In combination with a radio-receiver set having an aperiodic antenna circuit containing a radio frequency choke, with an untuned grid circuit connected across said choke, a tuning attachment for said set comprising a tuning element independent of said choke, means for quickly conductively attaching said tuning element to the antenna and the grid circuits, and {means for adjusting the tuning element to bring the grid'and the antenna circuits simultaneously into resonance, said tuning element comprising a variable capacitance and a variable inductance conductively connected together and variable in unison by said adjusting means.

3. In combination with an aperiodic antenna circuit for radio signaling having a radio frequency path therein of high effective resistance and a grid circuit conductively coupled thereto across the said path, of a variable tuning element independent of said path and comprising a condenser and an inductance connected in series across the said path to bring the combined grid circuit and cuit into resonance at a desired radio frequency, said tuning element having a neg1igible radio frequency efiective resistance when tuned as compared to the choke, and adjustable to have a .high effective resistance at radio frequency so that the antenna circuit may cooperate substantially. aperiodically with the grid circuit.

In testimony whereof I hereto aflix my signature.

ORIN E MARVEL. 

